Recently, a vehicle has been provided with an air bag device at the front side of the vehicle (e.g. a driver seat, a passenger seat) in order to improve safety of an occupant in case of a collision. When the collision is generated on the vehicle due to a traffic accident, an air bag controller outputs an operating signal for igniting an inflator to an air bag actuator based on a detection signal from a collision detecting sensor, then the air bag device is quickly inflated.
In the above-described vehicles provided with the air bag device operating in case of the collision for the safety of the occupant, there is a vehicle provided with the plural air bag devices and selectively operates the air bag devices in response to a direction of the collision. In this case, the air bag controller has to determine accurately whether the occupant sits on the seat or not in order to operate the air bag device properly. Particularly, with respect to the passenger seat, various situations can be generated, in which an adult sits on the seat, a child sits on the seat, or a child seat (hereinafter referred to as a CRS; Child Restraint System) is mounted on the seat, and the air bag controller needs to determine accurately whether the occupant sits on the seat.
With respect to an occupant weight detecting device for determining whether the occupant sits on the seat or not, various devices are known. For example, a device including plural cells for detecting pressure is known. In this device, the plural cells detects the pressure which is set by rows corresponding to a width direction of the sitting part and columns corresponding to a back-and-forth direction of the sitting part, and the device determines whether the occupant sits on the seat or not based on the pressure detected by the plural cells.
The known occupant weight detecting device including the cells is disclosed in a Japanese Patent Laid-Open Publication No.2001-180354. In this device, the sum of the pressure with respect to the width direction is calculated, and the device determines whether the occupant sits on the seat or not based on a template matching between the sum of the pressure and a predetermined pattern (template). In this device, two templates are provided corresponding to the sum of the pressure in two conditions in which the occupant regularly sits on the seat and the occupant sits on the seat at the front side (hereinafter referred to as a front-side sitting), and the device determines whether the occupant sits on the seat or the CRS is mounted on the seat by comparing two templates with the sum of the pressure detected by the cells.
Further, in the known occupant weight detecting device with the cells disclosed in a Japanese Patent Laid-Open Publication No.2002-87132, a determination value is corrected based on various calculated results, and the device finally determines whether the occupant sits on the seat or the CRS is mounted on the seat based on the corrected determination value. In this device, the device determines whether the occupant sits on the seat or not by a template matching as same with the above-described device.
However, since a build or a sitting manner of the occupant varies from person to person, in the above-described devices using the template matching, the device can perform the occupant determination based on only a limited condition. Further, though the CRS can be distinguished from the occupant based on a basic human-indicator template, the adult cannot be accurately distinguished from the child when the calculated determination value does not match with the basic human-indicator template and the front-side sitting template.
The present invention therefore seeks to provide an occupant weight detecting device capable of improving accuracy of determination about a state on a seat.